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Allotropes of Carbon and Intermolecular Forces

Allotropes of Carbon and Intermolecular Forces. IB Topic 4: Bonding. Carbon allotropes. pure carbon is covalently bonded in three of different forms (allotropes) graphite diamond fullerenes To buy lots of super duper expensive carbon allotropes, CLICK HERE. Graphite.

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Allotropes of Carbon and Intermolecular Forces

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  1. Allotropes of Carbon and Intermolecular Forces IB Topic 4: Bonding

  2. Carbon allotropes • pure carbon is covalently bonded in three of different forms (allotropes) • graphite • diamond • fullerenes • To buy lots of super duper expensive carbon allotropes, CLICK HERE

  3. Graphite • possesses a layer structure • the layers of carbon atoms are arranged in an repeating fashion

  4. Diamond • more compact structure and dense than graphite • one of the hardest materials known

  5. Fullerenes • highly stable chemically • most famous is the “buckeyball” • discovers awarded Nobel Prize in 1996 • over 1000 fullerene compounds have been made • composed of carbon atoms that form a hollow, cage-like structure • interesting feature of fullerenes is their ability to enclose other atoms

  6. Intermolecular Forces • forces that occur between molecules • much weaker than intramolecular (within the molecule) forces • it takes 464 kJ/mol to break the H-O bonds within a water molecule and only 19 kJ/mol to break the bonds between water molecules • the strength of the intermolecular forces determines the physical properties of the substance • melting, boiling, reacting, solubility, conductivity, volatility • this will be covered in next PowerPoint

  7. van der Waals forces

  8. van der Walls YouTube (:20) • also also known as London Dispersion Forces • even nonpolarmolecules have forces that hold them together • the distribution of electrons around an individual atom, at a given instant in time, may not be perfectly symmetrical • this can produce a temporary, instantaneous dipoles (polar molecule) • this can then induce a nearby molecule to be polar and therefore a very weak attraction between the two molecules • and so on, and so on…

  9. Sticky secret. Tiny hairs on geckos' feet help maximize contact with surfaces, allowing van der Waals forces to go to work.

  10. Dipole-Dipole Forces • attractive forces between the positive end of one polar molecule and the negative end of another polar molecule • must be in close proximity for the dipole-dipole forces to be significant • stronger than van der Waal's forces

  11. Hydrogen Bonding

  12. YouTube Hydrogen Bonding (1:40) • YouTube Hydrogen Bonding Video (:58) • a specific type of dipole-dipole type interactions • stronger than other dipole-dipole and/or dispersion forces • the hydrogen in a molecule (e.g. H-F, H-O or H-N) is bonded to a small, highly electronegative element (usually an F, O or N atom) on another molecule

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